There’s a decided spike in mid-2008, and a steady climb ever since. And if you check the trend for “app store”, it doesn’t even exist as a common search term until mid-2008.

I don’t know whether “app store” should be trademarkable. I’m leaning toward no, that it is too generic, and that they should only be granted trademarks for Something App Store — Mac App Store, iOS App Store, iTunes App Store, etc. But a lot of companies have gotten trademarks for pretty generic words when they’re used in a specific context. Steve Jobs has been using the word “app” for as long as I remember, easily back to the NeXT years. I remember thinking it always sounded awkward, too cutesy, whenever he said it, because it wasn’t in common usage.